redux reducer immutability test

redux-reducer-immutability-test.js

import test from 'ava';
import * as actionTypes from './your-action-types';
import reducer from './your-reducer';
import deepEqual from 'deep-equal';

test('reducer:immutability test', t => {
  const dummy = {};
  for (const action in actionTypes) {
    if (actionTypes.hasOwnProperty(action)) {
      const result = reducer(dummy, {type: actionTypes[action]});
      t.false(deepEqual(dummy, result, {strict: true}));
    }
  }
  t.end();
});

Be sure you always return with a new state object from your redux reducer (In case you're not using something like Immutabe.js).

haha nice trick.